The sensitivity of the human skin to the ultraviolet (UV) rays (UVR) of the sun is determined by the amount of the pigment, "melanin," contained within the skin. Many individuals with fair or light/white complexions (Skin Types I, II, III) burn because they do not produce sufficient melanin to protect the skin against sunburn. Moderately brown to dark skinned persons (Skin Types IV, V, VI) are not entirely protected form the deleterious effects of solar radiation. The different Skin Type classifications are characterized as follows:
Skin Type I: burns easily (freckles) and never tans; PA1 Skin Type II: burns easily and tans minimally; PA1 Skin Type III: burns moderately and tans gradually; PA1 Skin Type IV: burns minimally and tans well; and PA1 Skin Types V and VI: tans very well and rarely burns.
In addition to sunburn, long-term exposure to the sun, particularly for individuals who do not produce sufficient melanin such as Skin Types I, II, III can lead to premature aging of the skin and cutaneous cancer, usually basal cell, squamous cell carcinomas and malignant melanomas. Dark skinned persons do develop skin cancer but in small percentages, for example, malignant melanomas may occur in areas of the body where melanin levels are low, such as the palmar surfaces of the hands and plantar surfaces of the feet. Conditions such as allergic reactions, coarseness, dryness, mottling, flaccidity and blemishes are also effects of long-term exposure. To obviate these detrimental effects, experts in the field have suggested sun protection formulas having various combinations and percentages of chemical, physical and natural sunscreens, with the sun protective factor (SPF) ranging from 2 to 30 (minimal sun protection=2 and maximum sun protection=30).
Further, melanin precursors (i.e. tyrosine, tyrosinase and 3,4-Dihydroxy Phenylalanine (DOPA)) are included in suntan preparations to stimulate the production of melanin. Yet, each year these harmful or life-threatening toxicities are becoming more widespread because the problem still exists for those persons who do not genetically possess sufficient melanocytes (pigment cells) to produce enough melanin.
The pigment cell colors the skin by injecting melanosomes into keratinocytes. The keratinocyte carries pigment to the stratum comeurn where it is shed as melanin dust. Melanin provides effective protection against actinic damage of the sun. Notably, there exists an increased correlation between skin sensitivity to UV radiation and melanin content. The degree of sunburn reaction, prevalence of abnormal photosensitivity and the degenerative (aging) and neoplastic changes are reduced with increasing melanin pigmentation. This increased relationship is correlated to the distribution of melanosomes and quantity of melanin in the epidermis. The SPF estimates of melanin have been cited as 1.0-4.3 to 5 for Skin Types I through Skin Types V and VI, respectively.
The photoprotective role of melanin is related to its physical and biochemical properties. Melanin (a) scatters and degrades radiation to heat; (b) absorbs the radiation and promotes immediate oxidation reaction, and (c) quenches free radicals generated by UV radiation. Further, melanin in the human epidermis functions as a stable free radical. Because of its polyquinoid nature, melanin acts as an electron exchange polymer and therefore is capable of undergoing immediate photo-oxidation or darkening reaction. Melanin quenches the formulation of other types of damaging free radicals in the human epidermis upon exposure to UV radiation. Thus melanin serves as a scavenger for damaging non-melanin free radicals which may significantly contribute to its photoprotective role in individuals of Skin Types IV, V and VI.
The exposure to UV radiation itself produces a phototherapeutic advantage. Subsequent to three UV radiation exposures, Skin Types IV, V, VI become less likely to sunburn. However, Types I, II, III individuals develop very few melanized melanosomes. A melanin filter never develops in the stratum corneum resulting in an absence of melanin dust in the epidermis. Therefore, the need exists for the formulation of the topical application of melanin to provide an added amount of melanin in the skin to protect the human skin from the UV rays of the sun. Yet, dissolving melanin in solution or otherwise distributing melanin in a mixture suitable for topical application for delivery of melanin into the skin has been a difficult problem in the past. This problem was solved with U.S. Pat. Nos. 5,256,403 and 4,806,344.
The instant invention is significant in that it provides evidence at the molecular level of the effect of shielding of DNA against skin cancer-inducing lesions by sunscreening agents.
The instant invention, which is directed to a method for reducing pyrimidine photoproducts, uses methods and compositions previously described in U.S. Pat. Nos. 5,256,403 and 4,806,344 (which include natural sunscreening preparations produced by Frances Christian Gaskin, Inc.); however the claimed invention is not limited to using only the sunscreen preparations taught in U.S. Pat. Nos. 5,256,403 and 4,806,344 (herein incorporated by reference). Briefly, U.S. Pat. No. 4,806,344 teaches a composition and method of dissolving melanin in a composition for the purpose of photoprotection of human skin from exposure to ultraviolet radiation.
U.S. Pat. No. 5,256,403 teaches a solubilized melanin based compositions. The compositions consist of melanin, the active ingredient, and a substance to solubilize the melanin, blended together in a vehicle suitable for topical application.
The effects on environmental carcinogens, such as the increased levels of UVB in the biosphere resulting from ozone depletion, is a major human health concern. The natural sunscreening preparations produced by Frances Christian Gaskin, Inc. provide excellent protection to human skin against increased levels of the highly dangerous carcinogen, UVB. This invention is not limited to using sunscreen preparations produced by Frances C. Gaskin, Inc. (FCG) to reduce pyrimidine photoproducts but the inventor does prefer to use the sunscreen preparations as created by Frances C. Gaskin, Inc. to achieve this goal.